While the hereinafter disclosed invention has special application to the aeronautics industry in which large skin panels, frequently of compound curvature, as well as supporting structural assemblies and components are integrated by riveting, the teachings herein are equally applicable to other industrial environments.
The normal procedure for installing a rivet basically involves the distinct operations of hole preparation, rivet insertion and rivet upsetting. In general all three such operational events are carried out and completed in series sequence at each rivet location.
In earlier times a blacksmith carried out these steps by hand, utilizing a hammer, piercing tools and an anvil, rivet by rivet.
By later practice the components to be assembled were held in fixed position and manually operated power tools, such as electrical or air powered drills and riveting guns, were employed to effect the necessary riveting procedures, again rivet by rivet.
More recently, heavy, stationary, semi-automatic riveting machines have been developed to perform these operations with the work pieces being moved relative to the machine; the latter generally having a C-frame supporting the working tools and the work pieces being moved into the open throat of the C frame. Again the riveting procedure is accomplished rivet by rivet.
Under the latest technology, remotely controlled high-speed mobile machine centers or "robots", capable of presenting one or more drive spindles in selected spacial positions and adapted to drive a variety of machine tool attachments have gained industrial popularity. To date, however, the use of such robots for riveting procedures has been largely experimental and limited to situations where a single robot having multiple drive spindles is used to interconnect support components or frame members of a fixture held wing assembly for instance, using blind rivet fasteners. In operation the robot completes the entire riveting procedure, i.e., hole preparation, rivet insertion and fastening in series, at each rivet location, before proceeding to the next riveting point.
The above briefly described state of the art leaves much to be desired. In those instances where the work pieces are moved relative to a stationary riveting machine, maneuvering and positioning of heavy or bulky assembly components is slow and difficult with the size and/or shape of the parts being limited by the dimensions, particularly the throat capacity, of the riveting machine. In the reverse condition, where the work pieces are held stationary in a fixture and the work tools moved relative thereto, as in the case of the described roboticly controlled tools, serious problems are encountered in accurately positioning and repositioning the tools accompanied by a propensity for deforming and overstressing the assembled parts, resulting in inconsistent and dimensionally inaccurate end assemblies.